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Re: [OM] even more about the F280

Subject: Re: [OM] even more about the F280
From: "John Hermanson" <omtech@xxxxxxxxx>
Date: Wed, 24 Apr 2002 08:14:16 -0400
4, 4T, Ti curtain speed is usually 10.5  ms.
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John Hermanson  www.zuiko.com
Camtech, Olympus Sales & Service since 1977
21 South Lane, Huntington NY 11743-4714
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please call 1-800-221-3000
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----- Original Message -----
From: "Tom Trottier" <Tom@xxxxxxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Tuesday, April 23, 2002 9:38 AM
Subject: Re: [OM] even more about the F280


> Dear C.H.Ling
>
> 1.If 3T/4T full frame sync is at 1/60, wouldn't the curtain travel
>   time be ~14ms?
>
> 2.Does it start flashing when the 1st curtain opens and stop when
>   the 2nd curtain closes for all speeds shorter than 1/60? This would
>   imply a ~15ms time for 1/2000 up to ~27ms for 1/65, or flash
>   durations of 1/66 to 1/37, which differs from Olympus specs of 1/50
>   to 1/25. At 1/60, since the full frame is available, the flash
>   duration could be 1ms or less.
>
> 2.The GN for Super FP at 1/60 is 14.7, not the 28 that could be
>   expected. It seems that half the energy is lost using Super FP
>   instead of normal OTF.
>
> 3.The GN must be higher for the OM77 because the sync speed is
>   higher and more of the frame is illuminated at any shutter speed. But
>   why is it higher at 1/100 (15.6) than for the 4T at 1/60 (14.7)?
>
> 4.In auto mode, the shutter speed can vary infinitely, during the
>   exposure. Wouldn't this imply that the F280 must preserve enough
>   punch for the maximum exposure length, to keep the illumination even,
>   an amount not needed if the shutter speed turns out to be 1/2000. In
>   manual mode, though, the flash could be concentrated into the minimum
>   time, since it's known in advance. So why isn't the GN a little
>   different for the two modes?
>
> Has anyone tested this on a bench?
>
> tOM
>
> On Tuesday, April 23, 2002 at 15:22, C.H.Ling
> <olympus@xxxxxxxxxxxxxxx>
> wrote re "Re: [OM] even more about the F280" saying:
>
> > Hi Tom,
> >
> > Yes, the OM shutter curtain travel speed is fixed at around 11ms(?).
> > But you and many people ignored there is a second curtain. At 1/60s,
> > the 2nd curtain will only start when 1st curtain finish. The total
> > time could be around 22ms. Only at 1/2000s the two curtains action
> > time can be close to 11ms. The timing is just provide you a rough
> > idea, actually there could be 1 or 2ms between the 1st and 2nd curtain
> > at 1/60s and at 1/2000s there is a slit between the 1st and 2nd
> > curtain that could take 1 or 2ms to run.
> >
> > C.H.Ling
> >
> > Tom@xxxxxxxxxxxxx wrote:
> > >
> > > On what speeds does the F280 change it's duration and why?
> > > It seems to me the curtain slot always takes 1/60 at 1/60 and faster
> > > speeds, and at slower speeds, the flash could be done in 1/60 without
any
> > > problem.
>
> ------- Quidquid latine dictum sit, altum viditur -----------------
>    ,__@ Tom A. Trottier +1 613 860-6633 fax:231-6115
>  _-\_<, 758 Albert St.,Ottawa ON Canada K1R 7V8
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> ---------------------------------------------------------------------
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